My gmc jimmy 4x4 wants to start in high gear insteads of low

SOURCE: Got a 96 gmc jimmy auto shifter stuck in 3rd gear goes in 1 and 2 but nut n r or p so it wont start?

check yr gear linkages

SOURCE: 1998 GMC JIMMY 4X4 NOT ENGAGING

Sounds like a vacuum line is off

SOURCE: 1995 gmc jimmy will not shift out of 4wd high

sounds like the vacuum lines are either pinched or the vacuum pump is shot. try getting a mechanic look at the lines on and around your transfer case... also try checking the fuses for the 4wd selector. let me know how it goes

SOURCE: '95 GMC SUBURBAN

There is a actuator on the front axle. These are notorios for going bad. The new one will usualy come with a slug (round piece of metal) to install in front of the new actuator so it will engage your 4X4 faster. The factory setup was slow due to the pin having to move so far. The actuator will be towards the front of the vehicle on the passenger side of the differential.
Have a great evening

SOURCE: My 99 GMC Jimmy has the service 4X4 light on and

I own a Jimmy and have done quite a bit of 4 wheel drive repair on it.
The first thing i would check is the 4x4 selector switch. I know for a fact that these will throw a service 4x4 code if they are unplugged or shorted. They sell for 50-60$ or you may find one at a local salvage yard for cheaper. Taking this out and checking it only takes a few seconds, just simply pop the switch out of the dash with the edge of your pocket knife. After you get it out theres a few more tabs surrounding the back plate, and this is where the circuit board is located. I would inspect it visually to make sure nothing looks corroded and also take a sniff of it to insure there isn't a burnt smell. If it were the 4x4 actuator the lights would still illuminate on the selector switch, it just wouldn't engage the 4x4. You'r problem is all electrical trust me .